Thalamic astrocytic hamartoma and associated meningoangiomatosis in a German shepherd dog.

The present paper describes an astrocytic thalamic hamartoma associated with tectal meningoangiomatosis in a 3-month-old female German shepherd dog showing strabismus, opistotonus, circling, and fore limb hypermetria. MR images of the brain showed a well-defined intra-axial mass in the tectal region. The mass was hypointense to gray matter on T2-weighted images and hyperintense to gray matter on precontrast T1-weighted images. Histologically, glial cells arranged in a multinodular pattern characterized the mass. More caudally the lesion merged with subpial abnormal newly formed plaque-like shaped tissue characterized by thick branching bundles of spindle-shaped cells surrounding a central vessel. In the nodules, GFAP and vimentin were diffusely expressed. In the vascular proliferation Factor VIII-positive reaction was limited to endothelial cells while the remaining spindle-shaped cells were diffusely SMA-positive. The glial nodules did not express lysozyme and MAC387, nor neurofilaments and nestin.